RAID 10 with four 2 TB drives: mirrored stripes for speed and safety

How this is calculated

RAID 10 is the performance king among redundant RAID levels. Unlike RAID 5/6, there's no parity calculation penalty on writes, which makes random write performance dramatically better. This makes it the preferred choice for database servers, virtualization hosts, and any workload with heavy random I/O. The 50% capacity overhead is steep, but for performance-sensitive applications where downtime is expensive, it's the standard. Rebuild times are also much faster than RAID 5/6 because there's no parity to recalculate. The controller just copies data from the surviving mirror to the replacement drive.

Verdict

The 4x2 TB config yields 4 TB usable from 8 TB raw at the 50% capacity overhead that comes from striping across two mirrored pairs. Two factors make RAID 10 the performance pick among redundant RAID levels: writes have no parity calculation, so random write IOPS land 2-3x faster than RAID 5 on the same drives (every write hits the mirror directly without recomputing parity), and rebuilds just copy from the surviving mirror instead of recomputing parity across the whole array, which trims rebuild time and removes the second-failure window that haunts RAID 5. The fault tolerance is conditional: the array survives two failures if they hit different mirror pairs (a 67% probability with 4 drives) but loses data if both drives in the same pair fail. The capacity economics are why media-NAS buyers usually pick RAID 5 or 6 instead, while the write-IOPS economics are why database and VM-host buyers pick RAID 10.